Apparatus for making hollow plastic articles



Dec. 28, 1965 R. HAGEN I 3,225,382

APPARATUS FOR MAKING HOLLOW PLASTIC ARTICLES Filed Sept. 10, 1964 3 Sheets-Sheet 1 INVEN TOR fie/no/a f/ayan B Y WM H/ Dec. 28, 1965 HAGEN 3,225,382

APPARATUS FOR MAKING HOLLOW PLASTIC ARTICLES Filed Sept. 10. 1964 3 Sheets-Sheet 2 INVENTOR ffe/n o/c/ #056,? BY

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Dec. 28, 1965 R. HAGEN 3,225,382

APPARATUS FOR MAKING HOLLOW PLASTIC ARTICLES Filed Sept. 10, 1964 5 Sheets-Sheet 5 Fig. 7

INVENTOR fie/ho/d Hagen United States Patent 3,225,382 APPARATUS FOR MAKING HOLLOW PLASTIC ARTICLES Reinold Hagen, Hangelar uber Siegburg, Rhineland, Germany Filed Sept. 10, 1964, Ser. No. 395,410 Claims priority, application Germany, May 18, 1960, K 40,752 11 Claims. (Cl. 18--5) This invention relates to the manufacture of bottles and other hollow articles from plastic materials, and more particularly to apparatus for blowing such articles.

The term hollow articles is understood to comprise hollow bodies of any shape, provided the shape of a hollow embryo article, while in condition of plasticity, permits its being blown by fluid pressure to the desired final shape.

This application is a continuation-in-part of my copending application Serial No. 120,828, filed May 16, 1961, now abandoned and entitled Process for Making Hollow Plastic Articles.

For the purpose of the invention, any plastic material may be used which is capable of becoming softened and workable when heated to a relatively low temperature and which, while soft and workable, will permit a hollow embryo article to be expanded under fluid pressure to the desired shape. Blown articles, while cooling, become gradually rigid. For instance, low, medium and high density polyethylene, polystyrene, plasticized and nonplasticized polyvinyl chloride and nylon may be used.

A number of processes have heretofore been suggested to blow articles from plastic materials, ordinarily, but not necessarily, starting with material in form of tubing,

and numerous attempts have been made to provide suitable apparatus to carry out such processes.

One object of the present invention is to improve the manufacture of hollow plastic articles by blowing.

In producing bottles and other containers and other hollow articles from plastics, for instance, by extruding and blowing, an extrusion press and a sectional mold, preferably a two-section mold, are generally used. An open-ended tube may be extruded from an annular extrusion nozzle above the mold toward or into the space between the open sections of the mold to slip over a socalled blow pipe which projects into the open mold space from opposite the extrusion direction and in alignment with the extruded tube. As soon as a sufficient length of the open-ended tube is extruded, the mold sections are closed upon a portion of the tube, which causes the tube to be pinched shut by the mold sections near the nozzle. At the tube end remote from the nozzle, the material is pressed against and around the blow pipe. The blow pipe serves as a core to help form an opening in the article to be blown, for instance, the neck of a bottle, and it also serves to admit com-pressed air or any other fluid pressure medium into the closed tube portion within the closed mold. The fluid pressure medium admitted through the blow pipe expands the mold-enclosed tube portion against the wall of a mold cavity, where the molded article cools off and becomes rigid.

Thus, the cycle of operations of the referred to type of blow-molding machine using freshly extruded preforms generally comprises the steps of extruding a preform into the space between open mold sections, closing the mold sections and thereby forming a hollow embryonic article within the closed mold, the embryonic article being closed except for an opening for the admission of an inflating medium, inflating the embryonic article into contact with the walls of a mold cavity, allowing the inflated or blown article to cool and to become rigid 3,225,382 Patented Dec. 28, 1965 within the mold, opening the mold, and ejecting the rigid article.

It has been known for a long time that the period required by a freshly blown article to cool and to become rigid within a mold is relatively long and does not allow the mold to be as fully utilized as it is desirable. With the known apparatus to produce hollow plastic articles in a continuous operation, no full advantage could ordinarily be taken of the highest possible rates of extrusion. Generally, it was required to slow down the rate of extrusion to adjust same to the capacity of the facilities for forming the article. This reduces the otherwise possible output of molds and unfavorably influences the economy of blow-molding.

The primary object of the present invention centers about apparatus for the manufacture of hollow plastic articles by blowing, whereby the molding cycle is considerably shortened. The invention has for its purpose to do the extruding at the highest possible rate and to form the finished article as quickly as will be required by such rate of extrusion. Thus, my invention aims at speeding up and cheapening the manufacture of hollow plastic articles, that is, at an increase in output without an in crease in the initial and manufacturing costs.

To increase the rate of production rotary turrets have been suggested which carry a number of molds and are operated to move the open sections of one mold after the other into registry with an extrusion head. Such turntable constructions, however, in addition to calling for a plurality of molds, are complicated, of large dimensions, expensive, and require a large floor space.

To compensate for the long period needed by a freshly blown article to cool and become rigid within a mold and to make extrusion at any rate of speed possible, it has also been suggested to move a mold which is arranged underneath an extrusion nozzle, after the mold has been closed upon a portion of an extruded preform, downwardly away from the nozzle. In this way, the closed mold makes room for the plastic preform as it is extruded and as it lengthens in the downward direction.

The present invention rests on a new concept. When a plastic preform has been introduced in an open mold in a hot condition, that is, in condition of plasticity, and to the preform, after closing of the mold, has been expanded to the desired shape, the blown article does not solidify suddenly. Instead, the cooling and solidification take place gradually. In the course of solidification, that is, during the change from plasticity to rigidity, the plastic material passes through a number of more or less distinctive states. The solidification progresses from the outer wall of the blown article toward the inner wall, but there is also another, less pronounced, progress in the solidification, which take place from the inner wall of the blown article toward the interior of the wall. Actually, the outer layers of the blown article solidify before the interior of the wall does. I have found that a blown article, upon a preliminary solidification, reaches what will be referred to hereinafter as a presolidified, incompletely solidifled, or self-supporting condition. In this condition, the blown article appears cooled and solidified to such an extent that it can support itself and no longer requires the support of the mold. My invention has for one of its main purposes the provision of means which will make it possible to take advantage of this self-supporting property of a blown article. Bearing this in mind, it will be appreciated that the invention shortens the total molding cycle, which includes mold-closing time, blowing time, solidifying time, and mold-opening time, by decreasing the solidifying time. It will be understood that the self-supporting quality inherent in the structure and nature of a presolidified blown article can be enhanced by maintaining overpressure within the article.

The purpose of this invention of shortening the molding cycle and utilizing molds more fully cannot be served unless the mold used is opened as soon as the presolidified blown article has acquired self-supporting quality, and unless the article is removed from the mold and the removal of the article which is still liable to deformations is done safely. The article has to be given the opportunity to solidify to completion. Other objects of the present invention center, therefore, about means which will ensure the safe removal of presolidified blown articles from their molds and will make additional cooling and solidification possible. The premature removal of blown articles from a mold permits charging of the mold with preforms at a faster rate and thus a higher produo tion rate.

A further object of the invention is to provide an apparatus which is simple and inexpensive and does not require, as has already been indicated, a plurality of molds to cooperate, for instance, with a single extrusion nozzle, and yet ensures an increase in output.

Still further objects will be apparent from the following description.

The specification is accompanied by drawings in which:

FIG. 1 illustrates in a side elevational view, partly sectioned, an apparatus according to this invention;

FIG. 2 shows the apparatus of FIG. 1 in a plan view;

FIG. 3 is an elevation, partly sectioned, of another embodiment of the apparatus for practicing the invention;

FIG. 4 is a view similar to that of FIG. 3, but showing the apparatus in another operational position;

FIG. 5 is a view of a further modification of the apparatus of the invention;

FIG. 6 is a view similar to that of FIG. 5, but again showing another operational position;

FIG. 7 is a vertical section of still another modification of my apparatus, taken in the plane of the line 77 of FIG. 8; and

FIG. 8 is a horizontal section taken in the plane of the line 88 of FIG. 7.

Referring to the drawings in greater detail, and initially to FIGS. 1 and 2, there is an extruder 10 which is provided with an extrusion head 11. The latter is downwardly directed. A mold generally designated 12 cooperates with four cores 13, 14, and 16, which are fixedly mounted on a turntable 17, 90 apart from each other, to extend in a vertical upward direction. The cores are also used as blow pipes. In the condition shown, the blow pipe 16 is underneath an extrusion nozzle 18 of the extrusion head 11. The blow pipes 16 and 14, in positions I and III, respectively, are opposite each other, and a line connecting the positions I and III is parallel to the longitudinal axis of the extruder 10. Blow pipes 13 and 15, in positions II and IV, respectively, are shown along a line perpendicular to the line connecting positions I and III. The extrusion head 11 and the mold 12 are set apart 90. The mold is above the table 17 and is shownin open condition. The blow pipe 13 projects upwardly into the open space between the mold sections.

The arrangement of the four blow pipes is such that the blow pipe 16, while the revolving table 17 is turned through 90 in the direction of the arrow 19, moves away from the position I to assume the position H, the latter position having previously been that of blow pipe 13. The pipe 13 takes the place previously held by the blow pipe 14, position III. It will readily be understood that while the blow pipes 16 and 13 move to the position previously held by blow pipes 13 and 14, respectively, the blow pipe 14 moves to position IV, previously held by blow pipe 15, and the latter moves to the previous position of the blow pipe 16, position I. The blow pipes do not change the spatial relation one to the other, while they turn.

The apparatus of FIGS. 1 and 2 is operated by extruding a plastic tube 20 from the extrusion nozzle 18. The tube is open at its free or leading end. Since the blow pipe 16 extends from opposite the extrusion direction and in axial alignment with the extruded tube, the free tube end slips over the blow pipe 16. As soon as an adequate length of tubing has been extruded, two jaws 21 of a clamp grasp the tube at a place near the nozzle 18, and a tube segment is then severed from the parent body of plastic material in the nozzle. The severing is effected between the clamp 21, 21 and the underside of the nozzle 18, the severing means being not shown. The clamp 21, 21 helps the blow pipe 16 to support the severed tube segment. Any other suitable supporting means may be used instead of the clamp 21, 21. The table 17 is now turned and as the table turns both the blow pipe 16, which is carried by the table, and the clamp 21, 21 also turn. The clamp is actuated to grasp and to release and to reciprocate between the positions I and II by means which may be of any design and are not shown. Being held on its top by the clamp and at its bottom by the blow pipe 16, the severed tube segment is safely transported in a vertical condition along a 90 arc to arrive in the position II and to be received in the open space between the sections of the mold 12.

In FIG. 1, a severed tube segment 20 is shown to be slipped over, and vertically supported by, the blow pipe 13 and to be tightly held by the clamp 21, 21.

In the sequence of operations, the blow pipe 13 precedes the blow pipe 16. Upon arrival of a tube segment in the position II, the mold sections close upon the transported tube segment, whereby mold edges pinch the tube and convert the tube segment in a bubblelike formation closed at the top and open at the bottom. In the showing of FIGS. 1 and 2, it is the blow pipe 13 against which the tubular bottom portion of the pinched off bubble is press-molded. The bubble constitutes an embroyonic form of the hollow article to be blown. Next, compressed air or any other fluid pressure medium is blown through the blow pipe 13 into the bubble to expand the embryo form to the shape of the desired article.

When the mold 12 has been closed upon the tube segment 20 and an article has been blown therefrom, and when the mold has again been opened, the table 17 is again turned 90. The blow pipe 13 carrying the blown article 22 moves to the position IH.

It is an important feature of the present invention that the mold, contrary to established practices, is opened before the plastic material is fully solidified. Up to now, a blown article was removed from its mold after the article had solidified to such an extent that, for all practical purposes, it could no longer be deformed. The invention provides the removal of a blown article as soon as it is just self-supporting, that is, as soon as it can withstand a deforming action by its own weight. A most important feature of this invention is that the selfsupporting article, upon opening of the mold, is moved and held in vertical condition until it is fully solidified so that a tendency of the Weight of the article, which would otherwise cause deformation, will be safely checked. The movement is shown in FIGS. 1 and 2 to be horizontal but could take place in any other manner provided the article, as long as it is incompletely solidified but self-supporting, is kept vertically. The self-supporting property may be helped, as has already been stated, by maintaining interior overpressure.

The blown article 22, as it moves out of the mold toward the position III, a solidification station, is strong enough not to collapse but to support itself. While moving to position III, the article cools and solidifies further, and the article is given opportunity to cool still further and to solidify completely, while moving on through another 90 arc to the position IV, another solidification station. At the latter place, the article 22 is taken off its respective blow pipe.

The turntable rotates intermittently, each movement going through 90. It will be understood that the timing of the sequences involved is such that whatever is provided to occur during each 90 movement and during each subsequent standstill in each of the positions I to IV will be completed before the turntable turns again, except for the extrusion which is continuous. As for the extrusion, the free end of the tube that is being extruded will be ready to slip over a blow pipe when the latter, coming from the position IV, reaches the position I. In the position I, the jaws 21, 21 grasp the tube when a length of tube is to be severed and moved toward the position II. And in the position II, the mold which has opened to release a previously blown article closes upon the tube length just introduced and then opens again to release the article last blown.

In the embodiment shown in FIGS. 1 and 2, there are four blow pipes provided which pass one after the other through four working stations. In the position I, a length of tube is severed from the parent plastic body, and in the position II, the severed tube length is blown to the desired article. Thus, two positions or two blow pipes are available for additional cooling and solidifying, or about one half of the time needed for the whole cycle of operations is used for further cooling and solidification, in addition to the preliminary cooling and solidification that takes place within the mold. Due to the decrease in dwelling time of the blown article in the position 11 and due to the provision for further cooling in the positions III and IV before the blown article is removed from its supporting blow pipe, the highest possible rate of extrusion may be employed, making it at the same time possible to deal with the extruded material in a continuous manner.

The construction of FIGS. 1 and 2 uses a single extrusion press and a single mold. As for prior singlemold constructions, the present construction adds only three blow pipes and a turntable, which, in View of the relatively high initial cost of the extrusion press and mold, require no additional cost of any consequence, especially in the light of the increase in output ensured by the present construction. A turntable as shown may, of course, be replaced by a simple crosslike support or the like.

It will be apparent that the number of blow pipes may be varied, depending on prevailing conditions. A thickwalled blown article requires more additional cooling and solidifying time than a thin-walled article. The clamp 21, 21 has been stated to reciprocate between the positions I and II. It is to be understood that each blow pipe may be associated with a clamp of its own so that the clamps would rotate synchronously with the blow pipes.

Having now reference to the apparatus shown in FIGS. 3 and 4, the apparatus includes an extrusion machine 23 provided with two spaced nozzles 24 and 25. Centrally with respect to, and below, the nozzles is a two-section mold 226 which cooperates with two blow pipes 27 and 28. These blow pipes are carried by a common slide 29 and extend upwardly from the slide, the slide being guided by a rail 30 for reciprocation. The rail is parallel to a line connecting the extrusion nozzles 24 and 25 and lies in a plane that coincides with the parting plane of the mold. The mold opens and closes in directions perpendicularly to the parting plane of the mold and to the plane in which the rail 30 and the extrusion nozzles 24 and 25 lie.

In the working condition illustrated in FIG. 3, the blow pipe 28 extends in alignment with a tube which is extruded from the nozzle 25 so that a portion at the free end of the tube slips over the blow pipe 28. As soon as a sufficient length 31 of the tube is extruded, a clamp 32 or the like grasps the tube and severs the desired tube length from the parent plastic body in the nozzle 25. The severing means is not shown. It will be clear that a grasping device may be provided which will perform both the grasping and severing.

From FIG. 3, it will further be seen that the blow pipe 27 projects into a blown bottle 34 within the mold 26, the latter being shown in closed condition.

-As soon as the bottle 34 has been blown and has become self-supporting, the mold 26 opens and the slide 29 is moved to the left, when viewing toward the drawing, to assume the position shown in FIG. 4. The slide 29 carries the blow pipes 27 and 28 along. The blow pipe 27 takes the bottle 34 along which is in a presolidified state, and the blow pipe 28 brings the tube length 31 into the open mold space to be blown to the next bottle after the mold has closed and a fluid pressure medium has been admitted to the tube length. The arrangement of the mold 26 is such that the mold sections when open permit the movement of the blow pipes 27 and 28 through the open mold space.

Concurrently with the movements of the slide 29 and blow pipes 27 and 28 to the left, the clamp 32 as Well as another clamp 33 also move to the left. It will be apparent that the blow pipe 28 and the clamp 32 support the severed tube segment 31, while the blow pipe 27 supports and carries the blown bottle 34.

Upon arrival and complete solidification of the bottle 34- in he position shown in FIG. 4, the bottle is removed from the blow pipe 27 which has come to lie under the nozzle 24. The bottle may, for instance, be ejected by a short burst of air. A tube is now extruded from the nozzle 24 to slip with a portion at the leading end thereof over the blow pipe 27. The clamp 33 grasps the tube, and a length of tube is severed from the parent plastic material to be moved to the right while being supported by the blow pipe 27 and the clamp 33. This movement to the right is effected by a movement of the slide 29 to the right, that is, back to the position shown in FIG. 3.

By the time that the slide 29 is ready to be moved back to the right, a new bottle has been blown, which, upon opening of the mold and upon being supported by the blow pipe 28, also moves to the right. Along with the blow pipes 27 and 28 travels the clamp 33 and 32, respectively.

The blow pipes 27, 28 extend vertically and move horizontally. Thus, each freshly blown article, as long as it is in a presolidified state, is supported by a blow pipe to extend likewise vertically.

The construction of FIGS. 3 and 4 is intended for thinwalled bottles or containers. The time for additional cooling is short.

However, it is to be understood that the principle of the construction of FIGS. 3 and 4 may easily be adapted to longer additional cooling by providing a longer rail and setting the blow pipes farther apart, so that a blow pipe carrying a blown article will not come, upon leaving the blowing station, immediately below an extrusion nozzle but will pass through an intermediate station first. Applied to the showing of FIGS. 3 and 4, there would be either an idle station on each side of the mold between the mold and the extruding stations or just a longer travel distance.

If it is desired to extend the time of additional cooling, advantage may also be taken of an arrangement according to which the traveling paths of the cores extend between two levels of height. In an arrangement some what similar to that of FIGS. 3 and 4, the mold may be provided at a lower level, for instance, a level lower by the length of tube needed for the manufacture of the desired article, so that additional cooling time will be gained by moving a blow pipe together with an article in a freshly blown presolidified state thereon first sideways out of the open mold and then to the higher level. The movement between the two levels may be vertical, curved, or in any inclined direction. It is essential, however, that .the presolidified article be always kept in a vertical position.

In the construction of FIGS. and 6, a mold 35 is spacedly provided, vertically below an extrusion nozzle 36. The distance between mold and nozzle may, for instance, be equal to the length of tubing that is required for the blow-molding of the desired article. The distance may as well be shorter or longer. Two blow pipes 37 and 38, slidingly mounted on a slide 39, cooperate with the mold 35.

In the condition shown in FIG. 5, a blown bottle 40 appears in the closed mold, and the blow pipe 37 projects into the neck of the bottle. While the bottle is formed, a tube 41 .is extruded to suspend vertically downwardly into the space between the nozzle 36 and the mold 35. As soon as the blown botttle has become self-supporting, the mold is opened, and the slide 39 is moved from the right position of FIG. 5 to the left position of FIG. 6. As the slide 39 moves to the left, the blow pipes 37 and 38 move to the left, the former carrying the bottle 46 and giving the bottle additional cooling time and the opportunity to solidify more strongly, the latter entering the open mold 35. A clamp 42 grasps the tube 41. A segment of the tube supported by the clamp 42 is severed from the parent plastic body and lowered and introduced into the open mold, the free end of the tube segment being slipped over the blow pipe 38. When the mold closes upon the severed tube segment for the admission of a fluid pressure medium and for the formation of a new bottle, the clamp 42 moves up to be ready to seize the next severed tube segment.

The construction of FIGS. 5 and 6 affords principally the same extent of additional cooling and solidifying time as do the construction of FIGS. 1 and 2 and 3 and 4, respectively. The blown article has the same amount of time for additional solidifying as is required for the blow-molding and extrusion. However, in the case of FIGS. 3 and 4, the stations for additional solidifying coincide with the extrusion stations, so that the time for additional solidification is comparatively shorter.

In FIGS. 5 and 6, two pneumatically or hydraulically operated cylinders 43, 43 are shown, by way of example, to actuate the clamp 42.

The embodiment of the invention, illustrated in FIGS. 7 and 8, ensures a still greater increase in output. It includes an extruder 44 provided with three nozzles 45, 46, and 47. Each of these nozzles is associated with a twosectional mold of its own, the molds being designated 48, 49, and 50. The apparatus includes further two sets of three blow pipes each, designated 51, 52, 53 and 54, 55, 56, respectively. All of these six blow pipes are supported by a common slide 57, which is guided by rods 63, 63. A clamp 58 which is actuated by pneumatically or hydraulically operated cylinders 59, 59 serves to grasp extruded tubings 60, 61, 62 and to transport portions thereof, severed from the parent bodies of plastic in the nozzles, downwardly to introduce same into the open spaces between the sections of each of the molds.

The construction of FIGS. 7 and 8 is similar to that of FIGS. 5 and 6, except that in the former there are three molds rather than a single mold, and two sets of three blow pipes rather than two blow pipes or two sets of a single blow pipe. The operation of the apparatus of FIGS. 7 and 8 is also similar to that of the apparatus of FIGS. 5 and 6. The apparatus of FIGS. 7 and 8 extrudes three tubes 60, 61, 62 simultaneously to suspend freely downwardly and to make the leading end of each of the tubes slip over one of the blow pipes of one and the same set. After the molds have been closed over the three severed tube lengths, and the three embryo articles within the molds expanded, the blown articles, upon opening of the molds, are removed from the molds by moving the slide 57. When the slide, together with the blow pipes 51, 52, 53 and the blown articles carried by these blow pipes, is moved to the left, the blow pipes 54, 55, 56 move into the open mold spaces and are ready to receive fresh tubing lengths for the next blowmolding cycle.

It is believed that the construction and operation of the apparatus of the invention, and the many advantages thereof, will be understood from the foregoing detailed description. Some of the features and advantages are reviewed hereinafter.

The construction of FIGS. 1 and 2 uses four cores or blow pipes. The blow pipes pass one after the other through four stations, referred to hereinbefore as positions I, II, III, and IV. In the position I, a tube is extruded and a severed tube segment is received by a blow pipe. It will be understood that specific means for extruding and shaping preforms are no part of the present invention and that differently produced and shaped preforms may be used as well. However, since preforms have to be introduced in the mold in a hot and plastic state it appears that extruding preforms is the preferred thing to do. The molding is done in position II. Presolidified blown articles are moved to position III. While this movement to position III atiords such additional solidifying time as is proposed by this invention, and while in some cases a blown article may have solidified completely in the position III and may be removed in this position, the movement to position IV adds more additional solidifying time. It is to be noted that when preforms are extruded and when working with the construction of FIGS. 1 and 2 the extrusion is done in a place different from the blow molding place, which contributes to a reduction of the molding cycle which ordinarily includes the extrusion of the preform into the open mold space. The introduction of a severed length of preform, as provided in the construction of FIGS. 1 and 2, takes place at a higher speed than the introduction by extrusion. The construction of FIGS. 1 and 2 is most flexible. It permits the use of any number of blow pipes and any arrangement of extrusion machine, mold, and blow pipe stations. The table 12 is mounted to turn in a horizontal plane and to support the blow pipes in vertical positions. When moving from position to position, each blow pipe moves parallel to itself.

In the construction of FIGS. 3 and 4 and 5 and 6, respectively, there are two outer positions and a single center position. Each of the two blow pipes moves from only one of the outer positions to the common center position and back to the respective outer position.

In the case of the construction of FIGS. 3 and 4, a preform is extruded outside the mold space. As in the case of the construction of FIGS. 1 and 2, supporting means are needed which assist the blow pipe in transporting a severed tube segment from an extrusion station to the molding station and in properly placing the transported tube segment within the mold. Such supporting means, referred to in the description of FIGS. 1 to 4 as clamps, may be of any suitable design, as has been pointed out.

The construction of FIGS. 5 and 6 provides that the preform is extruded over a blow pipe which extends from opposite the extrusion nozzle into the open mold space.

It has been suggested, as has already been pointed out, to use more than a single mold to compensate for the time needed by a freshly molded article, to solidify while within a closed mold. The present invention uses a single mold in association with at least two cores, so that one of the cores, when supporting a presolidified article, may be removed from the open mold, and the other core may be introduced into the open mold space to permit the extrusion to continue at a high rate and the molding of the next cycle to be carried out.

In the embodiment of FIGS. 1 and 2, a single mold is used with four cores, and in the embodiments of FIGS.

- 9 3, 4 and 5, 6 a single mold is used with two cores. In the embodiment of FIGS. 7 and 8 three molds are used together with six cores, which corresponds to the association of a single mold and two cores.

The invention requires that the cores, however many may be employed, be always held and moved in vertical positions so that an incompletely solidified article be vertically supported and prevented from becoming bent or in any other way deformed.

The drawings and foregoing description deal with single-cavity molds, but it will be understood that molds having more than a single cavity may be used as well, provided the apparatus uses more than a single core for each of the cavities, making it possible for one core to be moved out of an open cavity space together with a presolidified blown structure for completion of the solidification while another core moves into the respective open cavity space. For instance, in FIGS. 7 and 8 three forms are shown. It will readily be appreciated that three cavities in a single form could be used instead.

In accordance with todays general industrial trends to increase production rates, the concept and development of machinery for making hollow plastic articles aims at using in one and the same apparatus more than a single mold. The present invention ensures an increase in output due to the reduction in dwelling time for a freshly molded article within a closed mold. With two molds in the same apparatus, the increased output is doubled, and with three and four molds, it is trebled and quadrupled, respectively.

The embodiment of FIGS. 5 and 6 includes means for extruding an open-ended tube and lowering a severed tube length to make a portion at the leading end thereof slip over a blow pipe which projects into an open mold space from opposite the extrusion direction and in alignment with the extruded tube. There are similar provisions in the embodiment of FIGS. 7 and 8 except that three tubes are extruded simultaneously instead of one. In both cases, the free end of a tube slips over a blow pipe projecting into an open mold space, ready to receive a portion of the tube at its free end. The freshly blown article is removed from the open mold with the aid of a blow pipe. In the embodiments of FIGS. 1, 2 and 3, 4, an open-ended tube is extruded over a blow pipe which then together with a severed tube length is horizontally transported into an open mold space. In each case, the blow pipe serves to act as a core to form an opening of the article being produced, to admit compressed air or any other pressure medium into the embryonic article, and to carry the blown article in a presolidified condition out of the open mold.

In this connection, reference is made to Patent 3,009,196 to N. Hagen, dated November 21, 1961, entitled Manufacture of Hollow Plastic Articles, to show that it is Within the scope of this invention to use blow pipes in any other possible way, provided the blow pipe is capable of carrying a presolidified article out of an open mold for completion of the solidification. According to the aforementioned patent, a hollow formation is extruded to suspend vertically into an open mold space. The mold is closed about a segment of the hollow formation, leaving an opening open, and a blow pipe is then introduced in a rarnlike fashion into said opening and admits fluid pressure to the fully enclosed segment. Such blow pipe is used according to the present invention, upon opening of the mold, to carry a presolidified article in vertical position out of the open mold space. Another blow pipe is used in the same ramlike manner while the first mentioned blow pipe is outside the mold.

If in an arrangement of the type shown in FIGS. 5 and 6, for instance, two molds are used, two extrusion nozzles, two groups of two cores each, and two supports or two support units are used. With three molds, the number of parts multiplies accordingly. The operation of such assemblies will be clear from the description of the operation of the apparatus of FIGS. 5 and 6.

The type of apparatus shown in FIGS. 3 and 4 may be used in multiple arrangements as well.

It will be apparent that while I have shown and described my invention in a few forms only many changes and modifications may be made without departing from the spirit of the invention defined in the appended claims.

I claim:

1. Apparatus for the manufacture of hollow articles from plastics, comprising at least a single mold including opposing sections to be closed and opened, the closed mold defining at least a single cavity conforming in shape to the article to be formed and being adapted to enclose an inflatable embryo article to be blown into molding contact with said cavity, at least two cores, each of said cores being adapted to cooperate with said mold separately and alternately, and a support having said cores spacedly mounted thereon to extend vertically, said support being movable so as to move said cores parallel to themselves and thus in vertical condition, said support and cores being arranged so that on moving the support one of said cores will enter between said mold sections when open, while the other of said cores will leave the open mold, said one core being adapted to extend from outside the closed mold into said mold-enclosed embryo article, said other core being adapted to support a blown article in an incompletely solidified but self-supporting state so *as to solidify to completion outside the mold.

2. The apparatus according to claim 1, wherein said opposing mold sections meet in a parting plane, and said cores are mounted on said support at points of a circle and, on moving the support, travel along said circle, the circle being substantially tangent to the parting plane.

3. In the apparatus according to claim 1, the support being arranged for reciprocal movements in a horizontal plane.

4. In the apparatus according to claim 1, two cores, two extrusion nozzles, one of said nozzles to extrude at any one time a preform of the plastic material used to suspend vertieally and to have an end portion of the preform slip over one of said cores, said mold being provided between said two extrusion nozzles, means to support segments of said two preforms at the trailing ends thereof near the extrusion nozzle, and means to sever said segments from the parent plastic bodies in said extrusion nozzles, said sup-port being arranged for reciprocal movements, said cores being arranged so that while said one core enters the open mold space the other core comes below one of said extrusion nozzles.

5. In the apparatus according to claim 4, said supporting means including individual means for each of said cores.

6. In the apparatus according to claim 1, an extrusion nozzle to extrude a preform of the plastic material used to suspend vertically, means to successively support segments of said preform at the trailing ends of said segments near said extrusion nozzle, means to sever said segments from the parent plastic body in said extrusion nozzle, and means to actuate said supporting means, thereby moving a segment together with said supporting means into the open space between said mold sections.

7. In the apparatus according to claim 6, said support being arranged so that while one of said cores moves into the open mold space to receive an end portion of one of said segments the other core moves out of said mold space.

8. In the apparatus according to claim 6, said supporting means being mounted to be vertically reciprocal.

9. Apparatus for the manufacture of hollow articles from plastics, comprising at least a single mold including opposing sections to be closed to meet in a parting plane and to be opened, the closed mold defining at least a single cavity conforming in shape to the article to be formed and being adapted to enclose an inflatable embryo article to be blown in molding contact with said cavity,

at least two cores, each of said cores being adapted to separately cooperate with said mold, and slide means mounted for reciprocal motions, said cores being spacedly secured on the slide means to extend vertically and upwardly, said slide means causing, on being reci-procated, said cores to move parallel to themselves and thus in Vertical condition, said slide means and cores being arranged so that on moving said slide means one of said cores will at any one time enter between said mold sections when open, while the other of said cores will leave the open mold, said one core being adapted to extend from outside said closed mold into said mold-enclosed embryo article, said other core being adapted to support a blown article in an incompletely solidified but self-supporting state so as to solidify to completion outside the mold.

'10. In the apparatus according to claim 1, at least two molds, at least two extrusion nozzles to simultaneously extrude as many preforms of the plastic material used as there are extrusion nozzles, each nozzle to extrude a preform downwardly, the number of molds being the same as that of the preforms, and at least two groups of two cores each, said support being constituted by at least two units, each of said units having two cores spacedly mounted thereon to extend vertically, each unit and the group of two cores mounted thereon being arranged so that while a core of said group moves into an open mold space to support a free end portion of an extruded preform the other core of said group moves out of said mold space.

11. In the apparatus according to claim 4, at least two molds, at least two assemblages of two extrusion nozzles each, and at least two groups of two cores each, a nozzle of each of said assemblages to extrude at any one time a preform to suspend vertically and to have an end portion of said preform slip over a core of one of said groups, means to support and sever segments of the preforms, said support being constituted by two units, each of said units having one of said core groups mounted thereon, the cores of each of said groups being arranged so that while one core of a group enters the open mold space the other core of the same group comes below a nozzle of one of said assemblages.

References Cited by the Examiner UNITED STATES PATENTS 2,783,503 3/1957 Sher-man 185 X 2,864,124 12/1958 Strauss 185 2,978,745 4/1961 Langecker 18-5 X FOREIGN PATENTS 746,505 3/1956 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

WILLIAM J. STEPHENSON, Examiner. 

1. APPARATUS FOR THE MANUFACTURE OF HOLLOW ARTICLES FROM PLASTICS, COMPRISING AT LEAST A SINGLE MOLD INCLUDING OPPOSING SECTIONS TO BE CLOSED AND OPENED, THE CLOSED MOLD DEFINING AT LEAST A SINGLE CAVITY CONFORMING IN SHAPE TO THE ARTICLE TO BE FORMED AND BEING ADAPTED TO ENCLOSE AN INFLATABLE EMBRYO ARTICLE TO BE BLOWN INTO MOLDING CONTACT WITH SAID CAVITY, AT LEAST TWO CORES, EACH OF SAID CORES BEING ADAPTED TO COOPERATE WITH SAID MOLD SEPARATELY AND ALTERNATELY, AND A SUPPORT HAVING SAID CORES SPACEDLY MOUNTED THEREON TO EXTEND VERTICALLY, SAID SUPPORT BEING MOVABLE SO AS TO MOVE SAID CORES PARALLEL TO THEMSELVES AND THUS IN VERTICAL CONDITION, SAID SUPPORT AND CORES BEING ARRANGED SO THAT ON MOVING THE SUPPORT ONE OF SAID CORES WILL ENTER BETWEEN SAID MOLD SECTIONS WHEN OPEN, WHILE THE OTHER OF SAID CORES WILL LEAVE THE OPEN MOLD, SAID ONE CORE BEING ADAPTED TO EXTEND FROM OUTSIDE THE CLOSED MOLD INTO SAID MOLD-ENCLOSED EMBRYO ARTICLE, SAID OTHER CORE BEING ADAPTED TO SUPPORT A BLOWN ARTICLE IN AN INCOMPLETELY SOLIDIFIED BUT SELF-SUPPORTING STATE SO AS TO SOLIDIFY TO COMPLETION OUTSIDE THE MOLD. 